HTML email allows the sender to properly express quotations (as in inline replying), headings, bulleted lists, emphasized text, subscripts and superscripts, and other visual and typographic cues to improve the readability and aesthetics of the message, as well as semantic information encoded within the message, such as the original author and Message-ID of a quote.

Long URLs can be linked to without being broken into multiple pieces and text is wrapped to fit the width of the user agent’s view-port, instead of uniformly breaking each line at 78 characters as defined in RFC 5322, which was necessary on older text terminals. It allows in-line inclusion of tables, as well as diagrams or mathematical formula as images, which are otherwise difficult to convey. The adoption of HTML-capable email clients is now nearly universal, with less than 3% reporting that they use text-only clients. A smaller number, though still the majority, prefer it over plain text.